You are here

Mathematical Treasure: Galileo's Discovery of Moons of Jupiter

Author(s):

Frank J. Swetz (Pennsylvania State University)

Galileo Galilei (1564-1642) wrote his works in Italian. One of his tracts that was translated into Latin for wider scientific distribution was Tractatus De Proportionum Instrumento (1612). The translator was Matthias Bernegger (1582-1640). This image is provided courtesy of the National Library of Florence (Biblioteca Nazionale Centrale di Firenze).

One of Galileo’s first acts after discovering the moons of Jupiter was to notify one of his patrons, Leonardo Donato, Doge (ruler) of Venice, of his findings. This sighting was truly historical, if not revolutionary, as it refuted the belief that all celestial bodies rotated about the earth – that is, the earth was not the center of the universe! This is a draft of the official letter he composed. Written in the month of August of 1609, it is the first document recording this scientific observation. The bottom of the manuscript contains Galileo's sketch of the moons and their relative positions. This manuscript is now housed at the University of Michigan Library, where you can read more about, including a translation into English.

The images above are supplied through the courtesy of the National Library of Florence and the University of Michigan Library, as indicated.